High oxide ion conductivity in Ca₁₂Al₁₄O₃₃

Abstract

Oxide ion conducting solids have much potential for use in fuel cells, sensors, oxygen pumps and gauges. Existing oxide ion conductors are essentially confined to a small group of ceramic oxides with structures related to fluorite, the most important examples being ZrO₂- and Bi₂O₃-related materials. There is a clear need for new oxide ion conductors with improved properties. We report measurements of the conductivity of Ca₁₂Al₁₄O₃₃, which indicate it to be an oxide ion conductor with bulk conductivity only 8–10 times less than that of yttria-stabilized zirconia. The structure of Ca₁₂Al₁₄O₃₃ is unrelated to the fluorite structure. The reasons for the high conductivity are not well understood but may be associated with the fact that the structure contains a mixture of anions, a three-dimensional aluminate framework and essentially free oxide ions.